Many types of passenger transport vehicles (such as aircraft, ships, buses, trains, and any other passenger transport vehicles) use vacuum toilets in order to flush septic waste, which is then delivered to a septic holding tank on board the vehicle. Such septic holding tanks are typically fluidly connected to the vacuum toilet system via a series of conduits, valves, and vacuum pumps in order to flush and route septic waste to the holding tanks. The vacuum created for the flushing action may either be via one or more vacuum pumps, or, in the case of an aircraft in flight, via a pressure differential. For example, aircrafts typically have a vacuum disposal system that applies a vacuum to pull waste media and flush water/spent water from toilets and/or sinks into an on-board waste water storage tank. The suction is generated either by the pressure differential between the pressurized cabin and the reduced pressure outside of an aircraft at high flight altitudes or by a vacuum generator at ground level or at low flight altitudes.
Although efficient, vacuum toilets create a loud noise level during the flush cycle, due to the amount of vacuum that needs to be applied in order to cause the septic waste to travel from the toilet basin to the holding tank. A loud flushing sound is created when the flush valve opens; the differential pressure is what forcefully draws the waste down the drain, and the pressure differential must be large enough to cause the waste to flow the entire distance from the toilet basin to the septic holding tank, which can be located quite far from the lavatory.
In addition to vacuum toilets, passenger lavatories also contain sinks for hand washing. For example, most commercial aircraft are equipped with galley and lavatory sinks. These sinks are typically intended for the disposal of fluid waste, soiled water from hand washing, and so forth. The spent water from sinks is referred to as “grey water,” as opposed to “black water” which has a urine or fecal component. (In addition to hand-washing water overflow from the lavatory, grey water can also include water from galley sinks. Fluids from the galley can contain items such as leftover portions of beverages and water from melting ice, or any other form of “used” or spent water that drains from the water system. Grey water can also drain from wash basins during hand washing, or any other instance in which water is soiled or loaded with waste, such as e.g., soaps, detergents, soils from hand washing, and so forth). These sinks are typically connected to small diameter drain lines (which can easily back up if clogged) and may either terminate at the aircraft drain mast for exhaustion to the atmosphere or may be delivered to a grey water holding tank. Although most large passenger transport vehicles are equipped with a grey water system for collecting, storing and ultimately disposing of grey water, providing a separate grey water holding tank is not always economical due to the additional weight that such systems add to the aircraft. (In the absence of special valves, such as those described by U.S. Pat. No. 7,533,426 titled “Grey Water Interface Valve Systems and Methods,” health standard guidelines for airlines require that septic water (“black water”) be vacuumed away separately from grey water because, if a back-up were to occur, sewage would be expelled from galley and lavatory sinks, as well as toilets, which could create a myriad of health problems.) Accordingly, the added expense of keeping grey and black water separate has generally been necessary.
The present inventors have sought to provide a way to re-use the grey water in connection with a toilet basin flush system. Although vacuum toilets use much less water than a typical gravity flow toilet, it is still desirable to find a way to re-use the spent/grey water rather than using fresh water for each flush cycle, due to cost and weight considerations of maintaining fresh water on-board. The present inventions have also sought to reduce the noise associated with vacuum flushing. They have further sought to provide new ways to vent plumbing conduits in order to help remove odors from the vacuum flushing system.